The present invention relates to a method of transferring articles.
In particular, the present invention relates to a method of transferring tobacco articles, such as cigarettes or packets of cigarettes, to which the following description refers purely by way of example.
In the tobacco industry, packets of cigarettes are known to be produced by forming groups of cigarettes, each defined by at least one layer of cigarettes; packing the groups in packing material to form the packets; sealing the packing material with an adhesive substance; and drying the adhesive substance to stabilize the packets.
Currently used systems for implementing the above method comprise one or more step-operated packing machines, i.e. of the type in which the cigarettes, fed in bulk to an input hopper of the packing machine, are withdrawn from the hopper and fed in groups of normally twenty cigarettes to a step-operated conveyor. The conveyor normally comprises a succession of pockets, which, as the conveyor moves forward in steps, are arrested successively at a loading station in front of the hopper to receive respective groups of cigarettes. Once formed and transferred onto the conveyor, the groups of cigarettes are transferred into seats on further conveyors defining a manipulating and packing path along which the groups are fed in steps to undergo said packing, sealing and drying operations.
Though extremely efficient and reliable, step-operated packing machines of the above type, like any step-operated mechanism, obviously have drawbacks: on the one hand, severe vibration, high noise level, and relatively high maintenance cost, mainly on account of the extremely high speed at which they are operated; and on the other, the fact that the speed of the conveyors can only be increased up to a given maximum limit.
To overcome the above drawbacks, and in view of the constant demand to increase the output of such conditioning machines, the current tendency is to produce machines in which all the conveyors operate continuously, to overcome the speed limit typical of step-operated conveyors.
Contrary to the above tendency, however, some operations, such as forming the layers or groups of cigarettes and drying the packets of cigarettes, would appear to be best performed in steps, which therefore means transferring cigarettes or a packet between a seat occupying a given position--in particular, a plate at the output station of a hopper, or a stationary seat on a step-operated conveyor--and a moving seat--in particular a seat on a continuously-moving conveyor.
This is the problem dealt with in European Patent No. 210,544, which relates to a chain transfer conveyor comprising a succession of pockets equally spaced along a chain, which, by virtue of a compensating system of movable pulleys, has a continuously-moving branch and a step-operated branch enabling groups of cigarettes to be transferred from the outlets of a hopper to a continuously-moving conveyor. The groups of cigarettes are transferred from the hopper outlets to stationary pockets along the step-operated branch, and from the pockets along the continuously-moving branch to the continuously-moving conveyor. The pockets on the conveyor must be arrested long enough to enable the cigarettes to be withdrawn from the hopper and inserted inside the pockets, which operations, though performed rapidly, call for the use of a step-operated pusher, the operating speed of which is limited, not only for mechanical reasons, but also to prevent subjecting the cigarettes to acceleration over and above a given limit.
The method proposed in the above patent fails to provide a satisfactory solution, by being based on the principle of arresting one branch of the transfer conveyor for as long as it takes to transfer groups of cigarettes from the hopper outlets to the respective pockets. As a result, the maximum speed of the transfer conveyor is no different from that of an ordinary step-operated conveyor, which limitation necessarily also affects the continuously-moving conveyors connected to it.